The proposed study aims at comparison of the metabolism and behavorial effects of six STP structurally related compounds, STP, DOET, 4-bromo-2,5-dimethoxyamphetamine, 4-fluoro-2,5-dimethoxyamphetamine, 2,4,5-trimethoxyamphetamine and 2,5-dimethoxyamphetamine, for gaining information on the effect of varying substitution in the para position on lipophilicity and plasma protein binding, and for correlation of metabolism with behavioral potency of these compounds. STP, its related compounds and their metabolites have been synthesized. Labeled compounds have been prepared by tritium-hydrogen exchange reaction for metabolic studies.